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Daggerboard - use of?

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G.R.F. View Drop Down
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Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 18 Sep 08 at 10:34pm
Originally posted by mike ellis

[

the best way to demonstrate hull steering on a dinghy is to try to bear
away with the boat heeled to leeward (away from you, then try the same
thing with the boat heeled to windward with all the controls the same.
Unless something very wierd happens with the Alto you should notice that it
is significantly easier when heeled on top of you.


This is what i was on about with windsurfers using "hull" steering the
opposite way to dinghies.



Well that's exactly what happens when you gybe a windsurfer with its plate
down, you weight the windward rail. I'd heard it works on dinghies, I shall
try it a little harder now on the bear off and round the gybe.
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Jack Sparrow View Drop Down
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Post Options Post Options   Quote Jack Sparrow Quote  Post ReplyReply Direct Link To This Post Posted: 19 Sep 08 at 8:41am
as for foil sweep this makes interesting reading... link

and here... link
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redback View Drop Down
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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 19 Sep 08 at 11:01pm
In GP14s and Scorpions (of which I have more experience) the centreboard is moved forward of vertical to give a bit of feel to the rudder which makes it easier to sail upwind in light winds.  As soon as the wind fills in the weather helm generated is a bit too much and the board is moved to vertical.
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G.R.F. View Drop Down
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Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 10:20am
So then we're all agreed now are we?

That when the bottom of the foil goes ahead of the top, in 'filled in' wind,
it acts in such a way that to continue efficiently it needs to be moved
aft..?

Yes?


So how do we now feel about planing skiffs with fixed foils when the nose
is lifted by the Spinnaker and or a wave and that action has the very same
effect?

Which is the point I was trying to make, and why skiffs in their present
incarnation are inefficient and will, like foiling moths, always have a
'speed ceiling' created by that inefficiency amongst others..(Like stern
drag or 'tail walking')

Interesting looking at things from a windsurfers perspective isn't it?

Edited by G.R.F.
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redback View Drop Down
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Post Options Post Options   Quote redback Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 5:10pm
You are right - ideally the board should sweep back and
even better reduce in area but at high speed we'd not
want all the turbulence caused by a centreboard case, so
we'll have to stick to a dagger. I really must remember
to get the board up a bit in a blow it might help reduce
that horrible twitchy feeling when we're doing over
15knots.
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Post Options Post Options   Quote dopamine Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 7:04pm
Originally posted by redback

You are right - ideally the board should sweep back and
even better reduce in area but at high speed we'd not
want all the turbulence caused by a centreboard case, so
we'll have to stick to a dagger. I really must remember
to get the board up a bit in a blow it might help reduce
that horrible twitchy feeling when we're doing over
15knots.


But, in my limited experience, the 4k really lifts its nose when the kite powers up. The RS800 sails much flatter and you can sense it wanting to pitchpole you.

Looks like the Alto pole is quite high, lifting the bow?
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Post Options Post Options   Quote alstorer Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 7:54pm
Originally posted by G.R.F.

So then we're all agreed now are we?

That when the bottom of the foil goes ahead of the top, in 'filled in' wind,
it acts in such a way that to continue efficiently it needs to be moved
aft..?

Yes?


So how do we now feel about planing skiffs with fixed foils when the nose
is lifted by the Spinnaker and or a wave and that action has the very same
effect?

Which is the point I was trying to make, and why skiffs in their present
incarnation are inefficient and will, like foiling moths, always have a
'speed ceiling' created by that inefficiency amongst others..(Like stern
drag or 'tail walking')

Interesting looking at things from a windsurfers perspective isn't it?


There's many trade offs to be had in boat design- that's why the 50knot mark is being chased by windsurfers, wierd solid wing one-tack specials and a massive foiling trimaran..

And whilst the Moth and Cherub types might be able to make use of this perspective, those of us on stricter classes just have to learn to live with what we've got.

But yes, interesting. As ever, no definitive answer.
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 8:44pm
Originally posted by G.R.F.

So then we're all agreed now are we?
Yes?

No. Its an over simplification which relates to certain specific circumstances, most especially an over flexible foil.

Originally posted by G.R.F.

why skiffs in their present
incarnation are inefficient


Oh good grief, here we go again... Skiffs are course racing boats. They're not intended to hit top speed on a limited number of directions only, so amazingly enough they're not as good at it as craft that are...

And the fastest course racing boat in the World are probably the solid wing sail C Class Cats, and according to the guys that sail them they struggle to get much past 20 knots... However they sail close to that *all the time* at amazing apparent wind angles... And in some repects, notably speed achieved as a multiples of wind strength, they are some of the most efficient water craft of all...

One of the dimmer witted statements you'll hear round the net is that boards aren't very efficient because whilst they can get damn close to 50knots, and will probably get there very soon (possibly beaten by the kiters), they can only do it is shedloads of wind. These folk claim that multihulls which can't handle the shedloads of wind but can do three times wind speed as opposed to not much more than one times are far more efficient than boards. Frankly that's ****, and I suspect you would agree.

Now extrapolate the logic...

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G.R.F. View Drop Down
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Post Options Post Options   Quote G.R.F. Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 8:45pm
50 knots has been broken this week or it was then they downgraded it
apparently
Kites

Edited by G.R.F.
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Post Options Post Options   Quote Black no sugar Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 08 at 8:46pm
Yeah but can you take your sandwiches on board?
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